Desensitization of liquid explosives



United States tary of the Navy No Drawing. Filed Aug. 3, 1960, Ser. No.47,335 Claims. (Cl. 149-88) (Granted under Title 35, US. Code (1952),see. 266) The invention described herein may be manufactured and used byor for the Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

This application relates generally to the ordnance art and is moreparticularly concerned with a new and improved mode of desensitizingliquid explosives to render them insensitive to detonation by accidentalmechanical shock.

Prior to this invention those explosives which were considered to bedangerously sensitive to mechanical shock, e.g., nitroglycerin, werediluted with a non-explosive material which was compatible with theliquid explosives. This method of desensitization was subject to onedisadvantage which detracted considerably from the usefulness of thedesensitized explosive. That is, a rather large amount of desensitizingagent was required to produce an explosive of sufiiciently lowsensitivity for safe handling and storage. Accordingly, explosivesdesensitized by this method were characterized by a marked reduction inthe explosive power. Persons using these liquid explosives were facedwith a dilemma which usually could be solved only by the unsatisfactorycompromise of employing a minimum amount of desensitizer so that theexplosive provided only marginal safety in its handling and use.

It is an object of this invention, therefore, to provide a mode ofdesensitizing liquid explosives which requires but a small amount ofdesensitizing agent to provide maximum safety.

Another object is the provision of a desensitized liquid explosivehaving high explosive power and providing maximum safety during handlingand storage.

Another object of this invention is to provide a liquid explosivedesensitized by a small quantity of a surface active agent.

These objects and many others will become more clearly apparent when thefollowing specification is read and understood.

This invention is founded upon the discovery that the addition of smallquantities of surface active agents to liquid explosives prevents theentry of shock and heat into the interior of the liquid explosivethereby preventing premature accidental detonation. By the term surfaceactive is meant a substance which tends to concentrate in the surfacephase of a mixture of itself and a liquid explosive or liquidpropellant. Thus, a substance of this type, when mixed with a liquidpropellant, will not be uniformly concentrated throughout the propellantbut will be more concentrated at the surface of the mixture. Theconcentration of the surface active agent at the surface tends toprevent the entry of heat and shock into the body of the propellant orexplosive.

These surface active agents are compounds of the type RCOOR R [COR and RR CO and R NO where: R is an alkyl containing from 2 to 5 carbons, R isan alkyl containing 4 to 6 carbons and R and R are alkyls containingfrom 4 to 8 carbons.

The class of surface active agents containing the nitro group does not,as might be expected, increase the sensitivity of a liquid explosivesuch as nitroglycerin or ethylene glycol dinitrate [EGDN]. On the otherhand,

atent 3,115,188 Patented Dec. 31, 1963 EXAMPLE I 82 parts by weight ofEGDN was poured into a beaker containing 18 parts by weight oftributyrin and the mixture was stirred gently. After complete mixing ofthe ingredients a five kilogram weight was dropped onto a small quantityof the explosive from a height of 60 centimeters. It was found that theexplosive was insensitive to detonation upon impact by the weight.

Generally, an explosive used in military applications must also beinsensitive to detonation by bullet impact. Accordingly, a second batchof EGDN was desensitized with tributyrate. It was found that in order tobe insensitive to the passage of 30 caliber machine gun bullets througha container holding the desensitized explosive an additional amount oftributyrin was required. When 70 parts of EGDN was desensitized with 30'parts tributyrin, the mixture was insensitive to bullet impact.

EXAMPLE II parts by weight of nitroglycerin (NG) was poured with gentlestirring into 20 parts by weight of tributyrin. The resultingdesensitized explosive was tested in the manner described in Example Iand was found to be insensitive to impact by a 5 kilogram Weight at 60centimeters.

A mixture of 30 parts tributyrin and 70 parts nitroglycerin was found tobe insensitive to bullet impact.

EXAMPLE III 75 parts by weight nitroglycerin was poured with gentlestirring into 25 parts of tricaproin. The material was tested and foundto be insensitive both to bullet impact and to detonation by a 5'kilogram weight falling from a height of 60* centimeters.

EXAMPLE IV 90 parts by weight of EGDN was added to 10 parts by weight ofdi-n-butyl sebacate in the manner of the immediately preceding example.The desensitized mixture was found to be insensitive to detonation by a5 kilogram weight dropped from 60 centimeters. To provide a bulletimpact insensitive mixture, 25 parts by weight of di-n-butyl sebacate to75 parts by weight of EGDN Were required.

EXAMPLE V A mixture of 30 parts of tricaprylin and 70 partsnitroglycerin was formed in the manner of the tests described inExamples I-IV. This desensitized mixture was found to be insensitive todetonation by the falling weight and by bullet impact.

EXAMPLE VI To 15 parts of tricaproin was added with gentle stirring 85parts of EGDN. The desensitized mixture was insensitive to impact by afalling 5 kilogram weight from a height of 60 centimeters.

The following table indicates the comparative sensitivities ofnitroglycerin desensitized by the prior art method of adding an inert[diethyleneglycol or triacetin] and nitroglycerin desensitized accordingto the principles of this invention with a surface active agent. Theheight indicated in millimeters is that height at which a falling 5kilogram weight will detonate the explosive 50% of the time and is astandard test for evaluating sensitivities of explosives. A highernumber indicates a less sensitive explosive; that is, one that is moresafe since it takes greater energy to detonate it.

Table 1 Percent desensitizer added to nitroglycerin Height (5 kilogramweight) mm.

Not surface active:

It is apparent that, by employing a surface active agent, thesensitivity of the liquid explosive is reduced to a safe level with acomparatively small amount of desensitizing agent. For example, 14.92%of the surface active agent tricaproin added to nitroglycerin results ina sensitivity of 600 millimeters while to produce the same sensitivitywith the conventional desensitizer, diethylene glycol, 22% desensitizeris required. The resulting explosive employing a surface activedesensitizer selected accordingly to the principles of this inventionwill result in an explosive composition which is safe to handle and yetcontains a large percentage of the explosive thereby increasing theexplosive power of the desensitized composition. Conversely, anexplosive of any given power can be made much more insensitive toaccidental detonation by employing a surface active desensitizer.

The invention is not to be construed as limited in any manner by theforegoing illustrative examples but is susceptible of many modificationsand alterations without departing from the spirit or scope thereof.Accordingly, the invention is to be defined only by the scope of theappended claims.

What is claimed is:

1. A composition consisting essentially of a liquid lower alkyl nitrateexplosive and from about 10% to about 30% of a liquid lower aliphaticpolybasic acid ester in which each esterifying portion of each moleculehas from three to seven carbon atoms in the chain.

2. A composition consisting essentially of a liquid lower alkylpolynitrate explosive and from about 10% to about 30% of a liquid loweraliphatic polybasic acid ester in which each esterifying portion of eachmolecule has from three to seven carbon atoms in the chain.

3. A composition consisting essentially of a liquid lower alkylpolynitrate explosive and from about 10% to about 30% of a liquid loweraliphatic polybasic acid ester having from 3 to 8 carbons in theacidportion exclusive of esterified acid groups, and in which eachesterifying portion of each molecule has from three to seven carbonatoms in the chain.

4. A composition consisting essentially of a liquid lower alkylpolynitrate having from 2 to 3 carbon atoms in the chain and from about10% to about 30% of a liquid lower aliphatic polybasic acid ester havingfrom 3 to 8 carbon atoms in the acid portion exclusive of esterifiedacid groups and in which each esterifying portion of each molecule hasfrom three to seven carbon atoms in the chain.

5. A composition consisting essentially of component [a] and from about10% to about 30% of component [[2]; component [a] being a memberselected from the group consisting of nitroglycerin and ethylene glycoldinitrate; and component [b] being a member selected from the groupconsisting of tributyrin, tricaproin,, trica-prylin and di-n-butylsebacate.

References Cited in the file of this patent UNITED STATES PATENTS1,999,828 Wiggam Apr. 30, 1935 2,096,451 Parodi-Delfino Oct. 19, 19372,668,102 Fisher et a1 Feb. 2, 1954

1. A COMPOSITION CONSISTING ESSENTIALLY OF A LIQUID LOWER ALKYL NITRATEEXPLOSIVE AND FROM ABOUT 10% TO ABOUT 30% OF A LIQUID LOWER ALIPHATICPOLYBASIC ACID ESTER IN WHICH EACH ESTERIFYING PORTION OF EACH MOLECULEHAS FROM THREE TO SEVEN CARBON ATOMS IN THE CHAIN.